Frame padding for wireless communications

ABSTRACT

Systems and techniques relating to wireless communications are described. A described technique includes obtaining data for a transmission to a wireless communication device(s), including one or more medium access control (MAC) data units that encapsulate data in a physical (PHY) frame, determining a length of a MAC layer pad based on a number of symbols associated with the PHY frame, including, in response to the length of the MAC layer pad being greater than zero, the MAC layer pad in the PHY frame after the one or more MAC data units, determining a length of a PHY layer pad based on remaining available bits in the PHY frame, including, in response to the length of the PHY layer pad being greater than zero, the PHY layer pad in the frame after the MAC layer pad, and transmitting the PHY frame to the wireless communication device(s).

CROSS REFERENCE TO RELATED APPLICATIONS

This disclosure claims the benefit of the priority of U.S. ProvisionalApplication Ser. No. 61/347,144, filed May 21, 2010 and entitled “11acFrame Padding”; the benefit of the priority of U.S. ProvisionalApplication Ser. No. 61/326,499, filed Apr. 21, 2010 and entitled “11acFrame Padding”; and the benefit of the priority of U.S. ProvisionalApplication Ser. No. 61/285,112, filed Dec. 9, 2009 and entitled “11acFrame Padding.” All of the above identified applications areincorporated herein by reference in their entirety.

BACKGROUND

This disclosure relates to wireless communication systems, such asWireless Local Area Networks (WLANs).

Wireless communication systems can include multiple wirelesscommunication devices that communicate over one or more wirelesschannels. When operating in an infrastructure mode, a wirelesscommunication device called an access point (AP) provides connectivitywith a network, such as the Internet, to other wireless communicationdevices, e.g., client stations or access terminals (AT). Variousexamples of wireless communication devices include mobile phones, smartphones, wireless routers, and wireless hubs. In some cases, wirelesscommunication electronics are integrated with data processing equipmentsuch as laptops, personal digital assistants, and computers.

Wireless communication systems, such as WLANs, can use one or morewireless communication technologies, such as orthogonal frequencydivision multiplexing (OFDM). In an OFDM based wireless communicationsystem, a data stream is split into multiple data substreams. Such datasubstreams are sent over different OFDM subcarriers, which can bereferred to as tones or frequency tones. WLANs such as those defined inthe Institute of Electrical and Electronics Engineers (IEEE) wirelesscommunications standards, e.g., IEEE 802.11a, IEEE 802.11n, or IEEE802.11ac, can use OFDM to transmit and receive signals.

Wireless communication devices in a WLAN can use one or more protocolsfor medium access control (MAC) and physical (PHY) layers. For example,a wireless communication device can use a Carrier Sense Multiple Access(CSMA) with Collision Avoidance (CA) based protocol for a MAC layer andOFDM for the PHY layer.

Some wireless communication systems use a single-in-single-out (SISO)communication approach, where each wireless communication device uses asingle antenna. Other wireless communication systems use amultiple-in-multiple-out (MIMO) communication approach, where a wirelesscommunication device, for example, uses multiple transmit antennas andmultiple receive antennas. A MIMO-based wireless communication devicecan transmit and receive multiple spatial streams over multiple antennasin each of the tones of an OFDM signal.

SUMMARY

The present disclosure includes systems and techniques for wirelesscommunications.

According to an aspect of the present disclosure, a technique forwireless communications includes obtaining data for a transmission to awireless communication device(s) via a physical (PHY) frame, includingone or more medium access control (MAC) data units, such as MAC protocoldata units (MPDUs), that encapsulate the data in a physical (PHY) frame,determining a length of a MAC layer pad based on a number of symbolsassociated with the PHY frame, including, in response to the length ofthe MAC layer pad being greater than zero, the MAC layer pad in the PHYframe after the one or more MAC data units, determining a length of aPHY layer pad based on remaining available bits in the PHY frame,including, in response to the length of the PHY layer pad being greaterthan zero, the PHY layer pad in the frame after the MAC layer pad, andtransmitting the PHY frame to the wireless communication device(s).

The described systems and techniques can be implemented in electroniccircuitry, computer hardware, firmware, software, or in combinations ofthem, such as the structural means disclosed in this specification andstructural equivalents thereof. This can include at least onecomputer-readable medium embodying a program operable to cause one ormore data processing apparatus (e.g., a signal processing deviceincluding a programmable processor) to perform operations described.Thus, program implementations can be realized from a disclosed method,system, or apparatus, and apparatus implementations can be realized froma disclosed system, computer-readable medium, or method. Similarly,method implementations can be realized from a disclosed system,computer-readable medium, or apparatus, and system implementations canbe realized from a disclosed method, computer-readable medium, orapparatus.

For example, one or more disclosed embodiments can be implemented invarious systems and apparatus, including, but not limited to, a specialpurpose data processing apparatus (e.g., a wireless communication devicesuch as a wireless access point, a remote environment monitor, a router,a switch, a computer system component, a medium access unit), a mobiledata processing apparatus (e.g., a wireless client, a cellulartelephone, a smart phone, a personal digital assistant (PDA), a mobilecomputer, a digital camera), a general purpose data processing apparatussuch as a computer, or combinations of these.

Details of one or more implementations are set forth in the accompanyingdrawings and the description below. Other features and advantages may beapparent from the description and drawings, and from the claims.

DRAWING DESCRIPTIONS

FIG. 1 shows an example of a communication process based on a framepadding technique.

FIG. 2 shows an example of a wireless network with two wirelesscommunication devices.

FIG. 3 shows an example of a wireless communication device architecture.

FIG. 4 shows an example of a spatial communication flow layout thatincludes MAC padding with end-of-frame signaling.

FIG. 5 shows an example of a transmission layout that includes MAC andPHY layer padding.

FIG. 6 shows an example of a transmission layout that includes MAC andPHY layer padding and end-of-frame signaling.

FIG. 7 shows an example of a spatial communication flow with long dataunit signaling and acknowledgements.

FIGS. 8A, 8B, and 8C show an example of communication flow layoutassociated with reduced block acknowledgement overhead.

FIGS. 9A and 9B show examples of a multi-user frame transmission layoutand associated acknowledgement responses.

FIG. 10 shows another example of a spatial communication flow layout.

FIG. 11 shows another example of a spatial communication flow layout.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

This disclosure provides details and examples of technologies forwireless local area networks, including systems and techniques forincluding frame padding in wireless transmissions and processingreceived transmissions that include frame padding. An example of a framepadding technique includes operating a wireless communication device todetermine MAC layer padding and PHY layer padding based on the number ofsymbols required to transmit the frame. Potential advantages of one ormore of the described technologies can include an increased systembandwidth, backwards compatibility with older standards, or both. Thetechniques and architectures presented herein can be implemented in avariety of wireless communication systems such as ones based on IEEE802.11ac.

FIG. 1 shows an example of a communication process based on a framepadding technique. A communication process implemented by a device suchan access point device or a client device can selectively include framepadding in a transmission. The inclusion of frame padding can bedetermined based on a number of symbols required for transmission. At105, the communication process obtains data for a transmission to awireless communication device(s). Obtaining the data for a transmissioncan include receiving data for two or more wireless communicationdevices from two or more sources such as applications, servers via anetwork, or storage devices. In some implementations, the communicationprocess arranges obtained data for transmission based on a SpaceDivision Multiple Access (SDMA) technique to concurrently transmit datato multiple devices. At 110, the process includes one or more MPDUs thatencapsulate the data in a PHY frame. Based on the obtained data, a MAClayer can generate an aggregated MPDU (A-MPDU) that includes the one ormore MPDUs and associated one or more MPDU delimiters. A PHY layer caninclude the A-MPDU into the PHY frame. In some implementations, the sizeof a MPDU delimiter is 4 octets. The PHY frame can include two or morespatially steered frames, with respective A-MPDUs, that are intended fortwo or more devices.

The communication process, at 115, determines a length of a MAC layerpad based on a number of symbols associated with the PHY frame. A MAClayer can generate the one or more MPDUs and the MAC layer pad. In someimplementations, a PHY layer can reduce the length of the MAC layer padto reduce a number of symbols required for the PHY frame. In someimplementations, a MAC layer can determine a MAC layer pad based on a4-octet boundary. A PHY layer, if required, can adjust the MAC layer padbased on a symbol boundary associated with the PHY frame. The PHY layercan add additional PHY layer bits such as PHY pad bits and convolutionalcode (CC) tail bits. At 120, the process includes, in response to thelength of the MAC layer pad being greater than zero, the MAC layer padin the PHY frame after the one or more MPDUs. In some implementations,the MAC layer includes the MAC layer pad into an A-MPDU.

Including the MAC layer pad in a frame can include including one or morepadding delimiters after the one or more MPDUs in an A-MPDU. A paddingdelimiter can be based on a MPDU delimiter format. Including the MAClayer pad in a frame can include including a MAC pad after the one ormore padding delimiters. A MAC pad can be an integer number of octets inlength that is less than four octets (e.g., 1, 2, or 3 octets in length,or 0 if not required). A MAC layer pad can include the one or morepadding delimiters and the MAC pad. A padding delimiter can include anend-of-frame (EOF) flag to inform a wireless communication device tostop receiving a PHY frame after a corresponding padding delimiter.Based on the EOF flag, a receiving wireless communication device canshut-off receiver circuitry to reduce power consumption.

At 125, the communication process determines a length of a PHY layer padbased on remaining available bits in the PHY frame. Determining theremaining available bits in the PHY frame can include accessing a lengthof the PHY frame, and accessing the length of an A-MPDU and the lengthof PHY tail bits to determine a length of a portion of the PHY frame tobe filed with a PHY layer pad. At 130, the process includes, in responseto the length of the PHY layer pad being greater than zero, the PHYlayer pad in the frame after the MAC layer pad. In some implementations,the communication process limits the length of the PHY layer pad to lessthan 32 bits. In some other implementations, the communication processlimits the length of the PHY layer pad to less than 8 bits. Tail bitscan be appended after the PHY layer pad.

At 135, the communication process transmits the PHY frame to thewireless communication device(s). Transmitting a PHY frame can includetransmitting two or more spatially steered frames that concurrentlyprovide data to two or more devices. The ends of the steered frames canbe aligned to facilitate transmissions of acknowledgements. One or moreof the steered frames can include MAC layer padding, PHY layer padding,or both. An amount of padding can be based on a maximum length that isdetermined by lengths of the steered frames. In some implementations,ends of the steered frames are aligned to have the same length, which issignaled by an omni-directional PHY signaling field that is common tothe steered frames.

A transmitting device can include one or more padding delimiters after alast non-zero-length A-MPDU subframe of the A-MPDU, where each of theone or more padding delimiters are four octets in length. Thetransmitting device can include a MAC pad after the one or more paddingdelimiters. A padding delimiter can indicate a MPDU length of zero. Insome implementations, the MAC pad is an integer number of octets inlength, which is less than four octets. In some implementations, a MACpad can be a partial EOF padding delimiter. The MAC layer pad caninclude the one or more padding delimiters and the MAC pad. In someimplementations, the one or more padding delimiters include anend-of-frame flag to inform a recipient device to stop receiving aremaining portion of the PHY frame.

A MAC layer pad can include a dword pad. In some implementations, atransmitting device includes a dword pad in the last non-zero-lengthA-MPDU subframe of the A-MPDU. At a transmitting device, a dword pad,padding delimiters, and the MAC byte pad can be added one by onewhenever there are still available bytes left in the PHY frame,exclusive of the tail bits. For example, the device can add a dword pad,byte by byte, until the last A-MPDU subframe reaches a 4-byte boundaryor reaches the last byte of the PHY frame. The device can add one ormore padding delimiters, one-by-one, whenever the remaining bytes arelarger than 4 bytes. The device, if the remaining byes are less than 4bytes, a MAC pad can be added to fill in one or more remaining bytes. Ata recipient device, a RX PHY processes the received PHY frame till thelast byte of the frame, excluding tail bits, and passes the receiveddata to a RX MAC. The RX MAC processes the received A-MPDU subframeone-by-one until detecting the EOF padding delimiter or until theremaining data after the last processed A-MPDU subframe is less than 4bytes.

In some implementations, a transmitting device makes a MAC layer padreach to a last 8-bit boundary of the PHY frame, exclusive of PHY tailbits in the PHY frame, and limits the length of the PHY layer pad toless than 8 bits. In some other implementations, a transmitting devicemakes a MAC layer pad reach to the last 32-bit boundary of the PHYframe, exclusive of PHY tail bits in the PHY frame, and limits thelength of the PHY layer pad to less than 32 bits.

A wireless communication device can include circuitry to access awireless communication interface and processor electronics configured toperform one or more techniques described herein. A wirelesscommunication interface can include circuitry to transmit and receivewireless communication signals.

FIG. 2 shows an example of a wireless network with two wirelesscommunication devices. Wireless communication devices 205, 207 such asan access point (AP), base station (BS), wireless headset, accessterminal (AT), client station, or mobile station (MS) can includecircuitry such as processor electronics 210, 212. Processor electronics210, 212 can include one or more processors that implement one or moretechniques presented in this disclosure. Wireless communication devices205, 207 include circuitry such as transceiver electronics 215, 217 tosend and receive wireless signals over one or more antennas 220 a, 220b, 222 a, 222 b. Wireless communication devices 205, 207 can communicatewith one or more types of devices (e.g., devices based on differentwireless communication standards) such as a high-throughout (HT) device(e.g., IEEE 802.11n based device) or a very high-throughout (VHT) device(e.g., IEEE 802.11ac based device).

In some implementations, transceiver electronics 215, 217 includeintegrated transmitting and receiving circuitry. In someimplementations, transceiver electronics 215, 217 include multiple radiounits. In some implementations, a radio unit includes a baseband unit(BBU) and a radio frequency unit (RFU) to transmit and receive signals.Transceiver electronics 215, 217 can include one or more of: detector,decoder, modulator, and encoder. Transceiver electronics 215, 217 caninclude one or more analog circuits. Wireless communication devices 205,207 include one or more memories 225, 227 configured to storeinformation such as data, instructions, or both. In someimplementations, wireless communication devices 205, 207 includededicated circuitry for transmitting and dedicated circuitry forreceiving. In some implementations, a wireless communication device 205,207 is operable to act as a serving device (e.g., an access point), or aclient device.

A first wireless communication device 205 can transmit data to one ormore devices via two or more spatial wireless communication channelssuch as orthogonal spatial subspaces, e.g., orthogonal SDMA subspaces.For example, the first wireless communication device 205 canconcurrently transmit data to a second wireless communication device 207using a spatial wireless channel and can transmit data to a thirdwireless communication device (not shown) using a different spatialwireless channel. In some implementations, the first wirelesscommunication device 205 implements a space division technique totransmit data to two or more wireless communication devices using two ormore spatial multiplexing matrices to provide spatially separatedwireless channels in a single frequency range.

Wireless communication devices, such as a MIMO enabled access point, cantransmit signals for multiple client wireless communication devices atthe same time in the same frequency range by applying one or moretransmitter side beam forming matrices to spatially separate signalsassociated with different client wireless communication devices. Basedon different signal patterns at the different antennas of the wirelesscommunication devices, each client wireless communication device candiscern its own signal. A MIMO enabled access point can participate insounding to obtain channel state information for each of the clientwireless communication devices. The access point can compute spatialmultiplexing matrices, such as spatial steering matrices, based on thedifferent channel state information to spatially separate signals todifferent client devices.

FIG. 3 shows an example of a wireless communication device architecture,which can include the various implementation details described herein. Awireless communication device 350 can produce signals for differentclients that are spatially separated by respective spatial multiplexingmatrices W_(i), e.g., steering matrices. Each W_(i) is associated with asubspace. The wireless communication device 350 includes a MAC module355. The MAC module 355 can include one or more MAC control units (MCUs)(not shown). The wireless communication device 350 includes three ormore encoders 360 a, 360 b, 360 c that receive data streams, from theMAC module 355, for N respective client devices. The encoders 360 a-ccan perform encoding, such as a forward error correction (FEC) encodingtechnique to produce respective encoded streams. Modulators 365 a, 365b, 365 c can perform modulation on respective encoded streams to producemodulated streams provided to spatial mapping modules 370 a, 370 b, 370c.

The spatial mapping modules 370 a-c can access a memory (not shown) toretrieve a spatial multiplexing matrix W_(i) associated with a datastream's intended client device. In some implementations, the spatialmapping modules 370 a-c access the same memory, but at different offsetsto retrieve different matrices. An adder 375 can sum spatially steeredoutputs from the spatial mapping modules 370 a-c.

An Inverse Fast Fourier Transform (IFFT) module 380 can perform an IFFTon an output of the adder 375 to produce a time domain signal. A digitalfiltering and radio module 385 can filter the time domain signal andamplify the signal for transmission via an antenna module 390. Anantenna module 390 can include multiple transmit antennas and multiplereceive antennas. In some implementations, an antenna module 390 is adetachable unit that is external to a wireless communication device 350.

In some implementations, a wireless communication device 350 includesone or more integrated circuits (ICs). In some implementations, a MACmodule 355 includes one or more ICs. In some implementations, a wirelesscommunication device 350 includes an IC that implements thefunctionality of multiple units and/or modules such as a MAC module,MCU, BBU, or RFU. In some implementations, a wireless communicationdevice 350 includes a host processor that provides a data stream to aMAC module 355 for transmission. In some implementations, a wirelesscommunication device 350 includes a host processor that receives a datastream from the MAC module 355. In some implementations, a hostprocessor includes a MAC module 355.

A MAC module 355 can generate a MAC Service Data Unit (MSDU) based ondata received from higher level protocols such a Transmission ControlProtocol over Internet Protocol (TCP/IP). A MAC module 355 can generatea MAC Protocol Data Unit (MPDU) based on a MSDU. In someimplementations, a MAC module 355 can generate a Physical Layer ServiceData Unit (PSDU) based on a MPDU. For example, a wireless communicationdevice can generate a data unit (e.g., a MPDU or a PSDU) that isintended for a single wireless communication device recipient. APhysical Layer Protocol Data Unit (PPDU) can encapsulate a PSDU.

A wireless communication device 350 can perform omni-directionaltransmissions that are intended for multiple client devices. Forexample, the MAC module 355 can operate a single data pathway betweenthe MAC module 355 and the IFFT module 380. The device 350 can performsteered transmissions that concurrently provide separate data tomultiple client devices. The device 350 can alternate betweenomni-directional transmissions and steered transmissions. In steeredtransmissions, the device 350 can transmit a first PPDU to a firstclient via a first spatial wireless channel and concurrently transmit asecond PPDU to a second client via a second spatial wireless channel.

With respect to the following figures, transmission signals can includeone or more legacy training fields (L-TFs) such as a Legacy ShortTraining Field (L-STF) or Legacy Long Training Field (L-LTF).Transmission signals can include one or more Legacy Signal Fields(L-SIGs). Transmission signals can include one or more VHT Signal Fields(VHT-SIGs). Transmission signals can include one or more VHT trainingfields (VHT-TFs). Examples of such training fields include a VHT ShortTraining Field (VHT-STF) and a VHT Long Training Field (VHT-LTF).Transmission signals can include different types of data fields such asVHT-Data fields.

FIG. 4 shows an example of a spatial communication flow layout thatincludes MAC padding with end-of-frame signaling. In a SDMA basedtransmission, a SDMA enabled device transmits VHT-Data segments to threerecipient devices via three spatial channels, respectively. VHT-Datasegments include respective aggregated MPDUs (A-MPDUs) 415 a, 415 b, and415 c. A-MPDUs 415 a-c each include one or more subframes.

Prior to transmitting the A-MPDUs 415 a-c, the SDMA enabled devicetransmits a L-SIG 405 and one or more VHT-SIGs 410 to the recipientdevices. The L-SIG 405 includes information that indicates a remainingduration of a PHY frame 401 (e.g., the number of symbols from the end ofthe L-SIG 405 to the end of a PPDU). For example, a client device candetermine the end of the frame 401 based on a length field and ratefield included in the L-SIG 405. The end of the frame 401 is based onthe longest VHT-Data segments in the SDMA based transmission. Note thatshorter VHT-Data segments align with the length of the longest VHT-Datasegment by including padding. In some implementations, a VHT-SIG 410includes information that indicates a remaining duration of the PHYframe 401 (e.g. from the end of the VHT-SIGs 410 to the end of a PPDU).Based on the depicted communication layout, the remaining durationindicated by the VHT-SIGs 410 is shorter than the remaining durationindicated by the L-SIG 405. In some other implementations, a VHT-SIG 410steered to a destination device indicates the length of the useful data,exclusive of the MAC layer padding, included in the A-MPDU transmittedto the destination device.

An amount of padding, if required, can be based on a remaining symbolduration, which is indicated by the L-SIG 405, the VHT-SIGs 410, orboth. The transmitting device, if required, inserts MAC padding 420 a,420 b after an end of an A-MPDU 415 b, c. An A-MPDU can include MACpadding. MAC padding 420 a, b can include end-of-frame (EOF) signalingsuch as one or more EOF padding delimiters. A padding delimiter can bebased on a MPDU delimiter format. In some implementations, an EOFpadding delimiter includes an EOF flag, a MPDU length field that is setto zero, a checksum, and a delimiter signature.

If required, the AP device inserts PHY padding 425 a, 425 b, 425 c afteran end of the A-MPDU 415 a-c, or, if present, after an end of the MACpadding 420 a, b. After the PHY padding 425 a-c, the AP inserts tailbits such as convolutional code (CC) tail bits 430 a, 430 b, 430 c.Based on an unpadded A-MPDU not reaching to a point within the lastsymbol of the frame 401, the AP device inserts MAC padding 420 a, 420 bafter the end of an unpadded A-MPDU 415 b, c. Based on the PHY padding425 b, c, and tail bits 430 b, c for client device communications in theframe 401, the position of the point can be different for each clientdevice communication. Thus, the amounts of MAC padding 420 a, b forrespective client device communications in the frame 401 can bedifferent.

Determining whether to add padding can include checking whether the endof the last subframe of an A-MPDU, exclusive of MAC layer padding 420 a,420 b, plus CC tail bits 430 b, 430 c is within the end of a last symbolboundary determined by a L-SIG 405 duration field, a VHT-SIG 410duration field, or both. In one padding technique, a TX MAC layer canpad an A-MPDU to a 32-bit boundary, e.g. pad the last A-MPDU subframe toa 32-bit boundary, keep adding padding delimiters until no more paddingdelimiters can be added, or both. Based on the A-MPDU, which may includepadding, the TX PHY layer appends a PHY pad, which is less than 32 bits,and PHY tail bits to extend the data to the last symbol boundary. Insome implementations, a TX MAC layer can pad the last A-MPDU subframe ofthe A-MPDU to a 32-bit boundary, keep adding padding delimiters untilall available bits in the corresponding PPDU are filled, or both. Basedon the MAC layer pad extending the A-MPDU to a 32-bit boundary, theA-MPDU plus PHY tail bits may exceed the last symbol boundary. The TXPHY layer can reduce the size of MAC layer padding until MAC layerpadding, a PHY pad, and PHY tail bits 430 fit in the last symbolboundary of a frame.

FIG. 5 shows an example of a transmission layout that includes MAC andPHY layer padding. A device can produce a transmission, which includes aPPDU 500 which was generated via multiple protocol layers, including aMAC layer and a PHY layer. The PPDU 500 includes an A-MPDU, whichcontains multiple subframes 515 a, 515 b, 515 n. For transmission, a TXMAC layer appends a MAC layer pad such as a MAC byte pad 520 to the endof the last subframe 515 n of the A-MPDU to pad to the end of the lastbyte boundary 530 in the PPDU exclusive of the tail bits. In some cases,the last subframe 515 n of the A-MPDU can include a padding delimiter;and, in some cases, one or more subframes preceding the last subframe515 n can include a padding delimiter. Based on a TX MAC layer output, aTX PHY layer appends data bits to the end of the MAC byte pad 520 tofill to the end of a symbol boundary 540, which is determined by aVHT-SIG 505 duration field. In this example, the TX PHY layer appends aPHY pad 535 after the end of the MAC byte pad 520 and appends tail bits545 after the end of the PHY pad 535. The size of the PHY pad 535 can beup to 7 bits in length (e.g., less than one byte in length); note thatthe A-MPDU, together with a service field 507 and tail bits 545, canoccupy all available bytes in a PHY payload. In another example based ona different ordering, the TX PHY layer appends tail bits after the endof the MAC byte pad and appends a PHY pad after the end of the tailbits. The combined size of the MAC byte pad 520 and the PHY pad 535 canbe less than 32 bits. The size of the MAC pad 520 can be 1, 2, or 3octets in length.

A transmitting device can determine whether to add padding based on oneor more conditions. Determining whether to add padding can includechecking whether the end of the last subframe 515 n of an A-MPDU,exclusive of MAC layer padding, plus tail bits 545 is within the end ofthe last symbol boundary 540 determined by a L-SIG 503 duration field ora VHT-SIG 505 duration field. In some implementations, a TX MAC layercan pad the last A-MPDU subframe 515 n to a 32-bit boundary and pass theA-MPDU to a TX PHY layer. In some implementations, the TX PHY layer canreduce the size of MAC byte pad 520 until the MAC byte pad 520, PHY pad535, and tail bits 545 extend to the last symbol boundary 540. In someother implementations, the TX PHY layer removes one or more padding bitsthat extend past the end of the last symbol boundary 540 less the lengthof the tail bits 545, and then adds the tail bits 545.

During a reception of the transmission 500, a RX PHY layer passestransmission data to a RX MAC layer until the last byte boundary 530.The RX PHY layer disregards the remaining content of the transmission500, e.g., PHY pad 535 and tail bits 545. In the RX MAC layer, the endof the last A-MPDU subframe 515 n can be determined by the length in thedelimiter of the last A-MPDU subframe 515 n. Based on the determinedend, the RX MAC layer removes the remaining content e.g., MAC byte pad520. In some implementations, a RX PHY layer passes received data to aRX MAC layer in 32-bit units until the remaining bits (excluding tailbits) are less than 8 bits or until the bits in the last symbol areexhausted. In some implementations, a RX MAC layer identifies the end ofthe last A-MPDU subframe based on the length in the delimiter of thelast subframe 515 n.

FIG. 6 shows an example of a transmission layout that includes MAC andPHY layer padding and end-of-frame signaling. A device can produce atransmission 600 that includes a MAC layer pad that contains EOF paddingdelimiters 610 a, 610 b and a MAC byte pad 620. The transmission 600includes an A-MPDU, which contains multiple subframes 615 a, 615 b, 615n. For transmission, a TX MAC layer appends one or more EOF paddingdelimiters 610 a, 610 b and a MAC byte pad 620 after the end of the lastsubframe 615 n of the A-MPDU to pad to the end of the last byte boundary630, exclusive of PHY tail bits 645. The MAC byte pad 620 is includedafter the last padding delimiter 610 b. In some implementations, an EOFflag is added to a delimiter of the last A-MPDU subframe 615 n. In someimplementations, each subframe 615 a, 615 b, including the last subframe615 n, in an A-MPDU is padded to a 32-bit boundary; this padding iscalled a dword pad, which can be 0, 1, 2, or 3 bytes in length. Thedword pad added to the end of the last A-MPDU subframe 615 n can beconsidered as a part of the MAC layer pad.

The TX PHY layer appends a PHY pad 635, which is typically less than onebyte, to the end of the MAC byte pad 620 and appends tail bits 645 afterthe end of the PHY pad 635. The size of the PHY pad 635 is based on thesymbol boundary 640 determined by a PHY signaling duration field, suchas a L-SIG 603 duration field or a VHT-SIG 605 duration field, andadditional PHY layer bits such as tail bits that are to be included intothe transmission 600.

Based on a reception of the transmission 600, a RX PHY layer passestransmission data to a RX MAC layer until the last byte boundary 630.The RX PHY layer removes the remaining content of the transmission 600,e.g., PHY pad 635 and tail bits 645, before passing data to the RX MAClayer. The RX MAC layer detects and removes the EOF padding delimiters610 a, 610 b. For example, once the RX MAC layer detects an EOF paddingdelimiter, the RX MAC layer can discard the remaining received dataafter the EOF padding delimiter and can signal the RX PHY layer to stopreceiving immediately to save power. In some cases, the RX MAC layerremoves the MAC byte pad 620. In some implementations, a received A-MPDUis processed, in multiples of 32-bits, until a remaining part is lessthan 32 bits. If the remaining part is not covered by either an A-MPDUsubframe or a padding delimiter, the remaining part (e.g., MAC byte pad620) is removed.

In some implementations, the last A-MPDU subframe in an A-MPDU caninclude a dword pad and one or more EOF padding delimiters. In thiscase, the MAC pad extends the A-MPDU to a 32-bit boundary. A device candetermine the size of a MAC pad based on one or more MAC padding rules.In a 32-bit boundary based MAC padding rule, the MAC pad is added toextend the last A-MPDU subframe to the last 32-bit boundary. At areceiving end, a RX PHY layer can pass received bits, excluding receivedtail bits, to a RX MAC layer using a 32-bit interface. The RX MAC layer,based on detecting an EOF delimiter in a MPDU, or detecting a paddingdelimiter, can remove the bits that follow the MPDU or the paddingdelimiter. If an EOF delimiter is not detected, the RX MAC layer candisregard the last received 32-bit not covered by an A-MPDU subframe.

In an 8-bit boundary based MAC padding rule, a MAC pad is added toextend the last A-MPDU subframe to the last 8-bit boundary. The devicecan include an EOF flag in the last subframe based on the last A-MPDUsubframe (including the last EOF padding delimiter) not reaching a32-bit boundary. At a receiving device, a RX PHY layer can pass receivedbits till the last 8-bit boundary to a RX MAC layer. The RX MAC layercan process bits received from a RX PHY layer until the remaining bitsare less than 8-bits. The RX MAC layer can disregard the remaining bits.

A device can signal the presence of an extended length PHY frame basedon a combination of fields in different locations in a PHY frame. Forexample, a device can include, in a first PHY signaling field (e.g., aL-SIG field), information to indicate a first length of the PHY frame,and include, in a second PHY signaling field (e.g., a VHT-SIG field),information to indicate a second length of the PHY frame. The second PHYsignaling field can be used to indicate an end of useful data in a PHYframe for a recipient device.

FIG. 7 shows an example of a spatial communication flow with long dataunit signaling and acknowledgements. A L-SIG 705 includes a rate fieldand a length field (L_LENGTH). Based on the L-SIG 705 rate fieldindicating a data rate of 6 Mbps, binary phase-shift keying (BPSK)modulation, and V2 code rate, there are 3 octets per symbol, whichprovides for a max L-SIG duration of 5.464 ms. Following the L-SIG 705,a VHT transmission can include a VHT-SIG-A 710 that signals a presenceof a PPDU longer than 5.464 ms, e.g., a VHT PPDU 701.

A VHT-SIG-A 710, in some implementations, includes an extended length(E_LENGTH) subfield to indicate a presence of a PPDU longer than 5.464ms. Based on a L_LENGTH and E_LENGTH, a VHT PPDU duration can beexpressed by:

$\left( {1 + \left\lceil \frac{{L\_ LENGTH} + {E\_ LENGTH}}{3} \right\rceil} \right) \times 4\mspace{14mu}{{µs}.}$For example, based on a 2-bit format for an extended length subfield,the length signaling bits of a PPDU are extended to 14 bits, which canindicate a max duration of 21.85 ms. However, a legacy device may beonly able to decode the L-SIG 705 of the transmission. If the PPDUduration is larger than 5.464 ms, a clear-to-send (CTS) message can betransmitted before the long PPDU transmission (e.g., longer than 5.464ms) to prevent legacy devices from transmitting during the long PPDUtransmission.

In some other implementations, VHT-SIG-A 710 includes a “Long PPDU”subfield, which can be 1-bit, to indicate a long PPDU. The “Long PPDU”subfield can be set to indicate a long PPDU duration (e.g., a PPDUduration being greater than 5.464 ms). Based on the “Long PPDU” subfieldindicating a long PPDU, a length field in the L-SIG 705 can be set basedon a rate lower than 6 Mbps (e.g. 2 Mbps or 1 Mbps), while the ratefield in L-SIG 705 is set as 6 Mbps. A VHT device, which is capable ofprocessing a long PPDU, can calculate a PPDU duration based on the L-SIG705 length field. For example, the VHT device can calculate a VHT PPDUduration based on (1+L_LENGTH)×4 μs, where L_LENGTH denotes a value inthe L-SIG 705 length field. A message such as a CTS-to-Self can betransmitted before the long PPDU transmission (e.g., longer than 5.464ms) to prevent legacy devices from transmitting during the long PPDUtransmission. Other long PPDU signaling techniques are possible.

An AP can use an implicit ACK policy to cause a first client (e.g., STA1) to transmit an acknowledgement response 730 (e.g. blockacknowledgement (BA) or an acknowledgement (ACK)) based on successfullyreceiving, via a spatial wireless channel, a VHT-Data segment 720 a,which can include a MAC header and a MAC payload. An AP can transmit ablock acknowledgement request (BAR) 740 to a second client (e.g., STA2). Based on the BAR 740 and successfully receiving, via a spatialwireless channel, a VHT-Data segment 720 b, which can include a MACheader and a MAC payload, the second client sends an acknowledgementresponse such as a block acknowledgement 750. In some implementations,an AP can initiate a BA with multiple Block ACK capable SDMA clients byusing an Add Block Acknowledgement (ADDBA) request and responseexchange.

A wireless communication system can use BA for acknowledgement of one ormore received MPDUs. A BA agreement setup and BA management can berequired. At a transmitting device, a BA queue is used for an active BAstream. At a receiving device, a scoreboard and reordering buffer areused for an active BA stream. A wireless communication system canprovide one or more mechanisms to reduce BA overhead for frames such asmanagement frames and A-MPDUs with a single MPDU.

FIG. 8A shows an example of communication flow layout associated withreduced BA overhead. A VHT device can transmit two or more VHT A-MPDUsto two or more respective VHT devices via two or more spatial wirelesschannels. Transmitted before a VHT A-MPDU, a VHT-SIG 815 a, 815 b caninclude a field that indicates whether a VHT A-MPDU is an A-MPDU with asingle MPDU (SM-A-MPDU). Rather than using signaling in a VHT-SIG, someimplementations can configure a device to detect a SM-A-MPDU based on alack of detecting a delimiter before detecting a MAC pad.

FIG. 8B shows an example of an A-MPDU layout associated with reduced BAoverhead. In this example, a device includes one or more null subframes845, such as an EOF padding delimiter, after a single A-MPDU subframe835 to indicate that the A-MPDU 830 has a single non-zero length MPDU(e.g., SM-A-MPDU). In some cases, the device can include a first MAC pad840 after the A-MPDU subframe 835 to make the A-MPDU subframe 835 reacha 32-bit boundary and before the one or more null subframes 845, e.g.,padding delimiters. The device can include a second MAC pad 841 afterthe one or more null subframes 845. The MAC pads 840, 841, if present,can be 1, 2, or 3 octets in length. MAC layer padding can include thefirst and second MAC pads 840, 814, and the one or more null subframes845.

FIG. 8C shows an example of an A-MPDU subframe layout associated withreduced BA overhead. A-MPDU subframe 850 can include signaling toindicate that the A-MPDU 830 has a single MPDU (e.g., SM-A-MPDU). Insome implementations, SM-A-MPDU signaling uses a 1-bit field in aleading field 855 of an A-MPDU subframe 850. In some otherimplementations, SM-A-MPDU signaling can reuse the EOF bit in thedelimiter to indicate that an A-MPDU is a SM-A-MPDU, with the EOF flagbeing set to 1 and the MPDU length being greater than 0. In some otherimplementations, SM-A-MPDU signaling uses a delimiter signature 860. Inyet some other implementations, SM-A-MPDU signaling uses a subfield in aMAC header 865 to indicate a SM-A-MPDU.

For a SM-A-MPDU transmission, a SM-A-MPDU can be transmitted without apreviously established BA agreement, e.g., an ADDBA exchange is notrequired. Queues other than BA queues can be used to buffer SM-A-MPDUs.An acknowledgement policy of a SM-A-MPDU can be set as Normal ACK. Forreceiving a SM-A-MPDU, a SM-A-MPDU can be accepted without an associatedand active BA stream. Scoreboard and BA reorder buffering are notrequired for a SM-A-MPDU requesting Normal ACK. Based on successfullyreceiving a SM-A-MPDU requesting Normal ACK, an ACK can be transmitted.If an A-MPDU includes a single MPDU, but there is no indication that theA-MPDU is a SM-A-MPDU, e.g. EOF flag in the delimiter of the single MPDUis not set, and the acknowledgement policy of the MPDU is set to Normalor Implicit ACK, a BA can be transmitted. In some implementations,management frames do not have an ACK policy field and cannot request BAas acknowledgement. Therefore, a management frame can use a SM-A-MPDUformat to request ACK as acknowledgement.

FIG. 9A shows an example of a multi-user frame transmission layout andassociated acknowledgement responses. In this example, only oneSM-A-MPDU 905 is included in a multi-user (MU) frame 910 transmission.The SM-A-MPDU 905 can be a management A-MPDU frame. The MU frame 910 caninclude two or more A-MPDUs with multiple MPDUs (MM-A-MPDUs 915 a, 915b). The SM-A-MPDU 905 indicates a request for a single acknowledgement,instead of a BA. Therefore, the SM-A-MPDU's ACK 925 cannot be polled bya BAR frame. The recipient of the SM-A-MPDU 905 can transmit an ACK 925immediately after a SIFS duration from the MU frame 910 without explicitpolling. In this example, a MU frame 910 can include at most oneSM-A-MPDU 905 because only one recipient can transmit immediately afterthe MU frame 910. Based on receiving BAR frames 920 a, 930 b, which aretransmitted after the MU frame 910, the recipients of the respective BARframes 920 a, 930 b can transmit BAs 935 a, 935 b for respectiveMM-A-MPDUs 915 a, 915 b. In some cases, the recipients of the MM-A-MPDUs915 a, 915 b can transmit respective BAs 935 a, 935 b based on a MUresponse schedule after the acknowledgement transmission from therecipient of the SM-A-MPDU 905. In some implementations, a poll framecan be used to poll a single acknowledgement from a recipient of theSM-A-MPDU 905 after the MU frame 910.

An Immediate Response Request (IRR) frame can be used to pollacknowledgement responses from SM-A-MPDU recipients, e.g., polling animmediate ACK for a management frame, immediate sounding feedback frame,or immediate data frames in a SM-AMPDU format. In some cases, theresponse transmission may not follow the rate of the IRR frame. Forexample, an IRR frame can be transmitted by using a non-HT PPDU with alow rate, while sounding feedbacks can be transmitted by using high-rateHT-PPDU or a VHT-PPDU.

FIG. 9B shows a different example of a multi-user frame transmissionlayout and associated acknowledgement responses. In this example, two ormore SM-A-MPDUs 955, 960 are included in a MU frame 970. The MU frame970 can include one or more MM-A-MPDUs 965. An IRR frame 985 a, 985 bcan be transmitted to poll immediate ACKs 990 a, 990 b from devicesreceiving the SM-A-MPDUs 955, 960. In this example, the recipients ofSM-A-MPDUs 955, 960 do not send an ACK based on a SIFS duration afterthe MU frame. A BAR frame 975 can be transmitted to poll a BA 980 from adevice receiving the MM-A-MPDU 965. Response types such as scheduled orsequential response can be used, e.g., a device receiving a SM-A-MPDUcan send an ACK based on response schedules or sequences.

FIG. 10 shows another example of a spatial communication flow layout. Adevice can add a PHY pad 1010 to a PPDU to ensure that PPDUs, in a SDMAtransmission 1005, have the same duration (e.g., the same number ofsymbols). The device can add the PHY pad 1010 to extend PHY data to theend of the last symbol boundary. L-SIG 1020 length and rate fields canbe used to indicate the common end (e.g. the number of symbols from theend of the L-SIG 1020 to the end of the PPDUs) of a group of PPDUs inthe SDMA transmission 1005. A steered VHT-SIG 1050 a, 1050 b can be setbased on a size of a corresponding PSDU to assist a receiving device todetermine the end of the PSDU and remove the PHY pad 1010. Based on thePSDU length, the receiving device can stop receiving at the end of thePSDU and disregard the remaining PHY pad 1010 to save power. Note thatin this case, the PSDU includes the useful data, and is not required toinclude a MAC pad. The PHY pad 1010 covers the remaining available bits,exclusive of the tail bits, in the PPDU till the end of the last symbolboundary. The tail bits (not shown) are appended. In someimplementations, tail bits can be added after the PSDU and before PHYpad.

Length and duration information of steered data units, such as steeredPSDUs included in steered VHT-Data 1060 a, 1060 b can be included in oneor more fields of a SDMA transmission 1005. In some implementations, asteered VHT-SIG 1050 a, 1050 b field can include a field for the numberof 4-octets of a steered PSDU, a field for the number of symbols of thesteered PSDU, or both. In some other implementations, a service fieldcan include a field for the number of octets of a steered PSDU, a fieldfor the number of 4-octets of the steered PSDU, a field for the numberof symbols of the steered PSDU, or a combination thereof. An extendedservice field, in some other implementations, includes a field for thenumber of octets of a steered PSDU, a field for the number of 4-octetsof the steered PSDU, a field for the number of symbols of the steeredPSDU, or a combination thereof. The service field can include a checksumto protect against signal corruption and can include a full or partialdestination address (e.g., AID, MAC address, or BSSID) for a receivingdevice to decide whether to process the remaining frame. In someimplementations, length and duration information of steered data unitscan be included in a MAC frame element such as a MAC header, adelimiter, or a MPDU subframe.

Based on using a 4-octet unit for indicating a length of a steered PSDU,one or more PSDUs, in a MU frame, can be padded to a 4-octet boundary.The steered PSDU length indicates the PSDU 4-octet boundary. A receiverdecodes until a PSDU's 4-octet boundary and stops receiving the MUframe. An A-MPDU format can be used, and the last A-MPDU subframe can bepadded to a 4-octet boundary. Based on a PSDU with a Qword pad notexceeding the last symbol, the PSDU can be padded to a 4-octet boundary,which is indicated by the steered PSDU length field. Based on a PSDUwith a Qword pad that exceeds the last symbol, the PSDU can be padded tothe last octet; however, the steered PSDU length indicates the PSDUlength plus the Qword pad. A recipient device can detect that a PSDU ispadded to the last octet when finding that the steered PSDU lengthexceeds the last symbol boundary. In some implementations, a steereddata unit length indicates a length of a PSDU plus Qword pad. In someimplementations, a steered data unit length indicates a position of thelast 4-octet boundary.

FIG. 11 shows another example of a spatial communication flow layout. Asteered VHT-SIG field 1105 can indicate the end of useful data in acorresponding PSDU (e.g., end of useful data in an A-MPDU). After theend of useful data in a PSDU, there can be padding such as a MAC pad,PHY pad, or both. In some implementations, a steered VHT-SIG field 1105includes the length (e.g., number of octets, or number of 4-octets) ofuseful data in a corresponding PSDU. In some implementations, a steeredVHT-SIG field 1105 includes the duration (e.g. number of symbols) ofuseful data in a corresponding PSDU. As depicted by FIG. 11, a MAC pad,a PHY pad, and tail bits are appended to each A-MPDU. The L-SIG 1110 caninclude a length field, a rate field, or both to indicate the durationof a PPDU. In a MU frame 1100, multiple PPDUs have the same endingpoint, which is indicated by the L-SIG 1110.

A length field can be included in a steered VHT-SIG 1105 to indicate thenumber of octets or number of 4-octets of useful data included in acorresponding PSDU, exclusive of the padding and tail bits. Based on thelength field, a receiving device can stop receiving at the end of theindicated useful data to save power and disregard the remaining data. Insome implementations that are based on a length that represents thenumber of 4-octets, the length may indicate a 4-octet boundary whichexceeds the last symbol boundary; in this case, a receiving deviceprocesses till the last byte of a PPDU and discards the remaining datasuch as a PHY pad and tail bits.

In some implementations, a duration field can be included in a steeredVHT-SIG 1105 to indicate the number of symbols required to cover theuseful data in a corresponding PSDU. Based on this duration field, thereceiving PHY can stop receiving at the end of the indicated durationand discard the remaining data. The receiving MAC can determine the endof the useful data based on the last A-MPDU subframe passed from thereceiving PHY. In some implementations, a receiving MAC can determinethe end of the useful data based on a detected EOF padding delimiter.

A few embodiments have been described in detail above, and variousmodifications are possible. The disclosed subject matter, including thefunctional operations described in this specification, can beimplemented in electronic circuitry, computer hardware, firmware,software, or in combinations of them, such as the structural meansdisclosed in this specification and structural equivalents thereof,including potentially a program operable to cause one or more dataprocessing apparatus to perform the operations described (such as aprogram encoded in a computer-readable medium, which can be a memorydevice, a storage device, a machine-readable storage substrate, or otherphysical, machine-readable medium, or a combination of one or more ofthem).

The term “data processing apparatus” encompasses all apparatus, devices,and machines for processing data, including by way of example aprogrammable processor, a computer, or multiple processors or computers.The apparatus can include, in addition to hardware, code that creates anexecution environment for the computer program in question, e.g., codethat constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them.

A program (also known as a computer program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, or declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment. A program does notnecessarily correspond to a file in a file system. A program can bestored in a portion of a file that holds other programs or data (e.g.,one or more scripts stored in a markup language document), in a singlefile dedicated to the program in question, or in multiple coordinatedfiles (e.g., files that store one or more modules, sub programs, orportions of code). A program can be deployed to be executed on onecomputer or on multiple computers that are located at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

While this specification contains many specifics, these should not beconstrued as limitations on the scope of what may be claimed, but ratheras descriptions of features that may be specific to particularembodiments. Certain features that are described in this specificationin the context of separate embodiments can also be implemented incombination in a single embodiment. Conversely, various features thatare described in the context of a single embodiment can also beimplemented in multiple embodiments separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments.

Other embodiments fall within the scope of the following claims.

1. A method comprising: obtaining data for a transmission to a wirelesscommunication device; including one or more medium access control (MAC)data units in a physical (PHY) frame, wherein the one or more MAC dataunits encapsulate the data; determining a length of a MAC layer padbased on a number of symbols associated with the PHY frame; including,in response to the length of the MAC layer pad being greater than zero,the MAC layer pad in the PHY frame after the one or more MAC data units;determining a length of a PHY layer pad based on remaining availablebits in the PHY frame; including, in response to the length of the PHYlayer pad being greater than zero, the PHY layer pad in the PHY frameafter the MAC layer pad; and transmitting the PHY frame to the wirelesscommunication device.
 2. The method of claim 1, wherein the one or moreMAC data units are MAC protocol data units (MPDUs) that are included inthe PHY frame in an aggregated MPDU (A-MPDU), wherein including the MAClayer pad in the PHY frame comprises including one or more paddingdelimiters after a last non-zero-length A-MPDU subframe of the A-MPDU,wherein each of the one or more padding delimiters are four octets inlength, and including a MAC pad after the one or more paddingdelimiters, wherein the MAC pad is an integer number of octets inlength, which is less than four octets, wherein the MAC layer padincludes the one or more padding delimiters and the MAC pad.
 3. Themethod of claim 2, wherein the one or more padding delimiters include anend-of-frame flag to inform the wireless communication device to stopreceiving a remaining portion of the PHY frame.
 4. The method of claim2, wherein including the MAC layer pad in the PHY frame comprisesincluding a dword pad in the last non-zero-length A-MPDU subframe of theA-MPDU, wherein the MAC layer pad includes the dword pad.
 5. The methodof claim 2, wherein the one or more padding delimiters indicate a MPDUlength of zero.
 6. The method of claim 1, further comprising: making theMAC layer pad reach to a last 8-bit boundary of the PHY frame, exclusiveof PHY tail bits in the PHY frame; and limiting the length of the PHYlayer pad to less than 8 bits.
 7. The method of claim 1, furthercomprising: making the MAC layer pad reach to the last 32-bit boundaryof the PHY frame, exclusive of PHY tail bits in the PHY frame; andlimiting the length of the PHY layer pad to less than 32 bits.
 8. Themethod of claim 1, further comprising: including PHY tail bits in thePHY frame after the PHY layer pad.
 9. The method of claim 1, furthercomprising: including PHY tail bits in the PHY frame after the MAC layerpad, wherein the PHY layer pad is included after the PHY tail bits. 10.The method of claim 1, further comprising: generating, at a MAC layer,the one or more MAC data units and the MAC layer pad, wherein the MAClayer pad extends past a last symbol boundary of the PHY frame; andreducing, at a PHY layer, the length of the MAC layer pad at a PHY layerto not extend past the last symbol boundary of the PHY frame.
 11. Themethod of claim 1, wherein obtaining the data comprises receiving thedata for wireless communication devices, transmitting the PHY framecomprises transmitting spatially steered frames that concurrentlyprovide the data to the wireless communication devices, a steered frameof the steered frames includes the one or more MAC data units, the MAClayer pad, and the PHY layer pad, and ends of the steered frames arealigned to have the same length, which is signaled by anomni-directional PHY signaling field that is common to the steeredframes.
 12. The method of claim 1, further comprising: including, in afirst PHY signaling field, information to indicate a first length of thePHY frame; and including, in a second PHY signaling field, informationto indicate a second length of the PHY frame.
 13. An apparatuscomprising: circuitry to access a wireless communication interface; andprocessor electronics configured to obtain data for a transmission to awireless communication device via the wireless communication interface,include one or more medium access control (MAC) data units in a physical(PHY) frame, wherein the one or more MAC data units encapsulate thedata, determine a length of a MAC layer pad based on a number of symbolsassociated with the PHY frame, include, in response to the length of theMAC layer pad being greater than zero, the MAC layer pad in the PHYframe after the one or more MAC data units, determine a length of a PHYlayer pad based on remaining available bits in the PHY frame, andinclude, in response to the length of the PHY layer pad being greaterthan zero, the PHY layer pad in the PHY frame after the MAC layer pad.14. The apparatus of claim 13, wherein the one or more MAC data unitsare MAC protocol data units (MPDUs) that are included in the PHY framein an aggregated MPDU (A-MPDU), and wherein the processor electronicsare further configured to include one or more padding delimiters after alast non-zero-length A-MPDU subframe in the A-MPDU, wherein each of theone or more padding delimiters are four octets in length, and include aMAC pad after the one or more padding delimiters, wherein the MAC pad isan integer number of octets in length, which is less than four octets,wherein the MAC layer pad includes the one or more padding delimitersand the MAC pad.
 15. The apparatus of claim 14, wherein the one or morepadding delimiters include an end-of-frame flag to inform the wirelesscommunication device to stop receiving a remaining portion of the PHYframe.
 16. The apparatus of claim 14, wherein the processor electronicsare further configured to include a dword pad in the lastnon-zero-length A-MPDU subframe of the A-MPDU, wherein the MAC layer padincludes the dword pad.
 17. The apparatus of claim 14, wherein the oneor more padding delimiters indicate a MPDU length of zero.
 18. Theapparatus of claim 13, wherein the processor electronics are furtherconfigured to make the MAC layer pad reach to a last 8-bit boundary ofthe PHY frame, exclusive of PHY tail bits in the PHY frame, and limitthe length of the PHY layer pad to less than 8 bits.
 19. The apparatusof claim 13, wherein the processor electronics are further configured tomake the MAC layer pad reach to the last 32-bit boundary of the PHYframe, exclusive of PHY tail bits in the PHY frame, and limit the lengthof the PHY layer pad to less than 32 bits.
 20. The apparatus of claim13, wherein the processor electronics are further configured to includePHY tail bits in the PHY frame after the PHY layer pad.
 21. Theapparatus of claim 13, wherein the processor electronics are furtherconfigured to include PHY tail bits in the PHY frame after the MAC layerpad, wherein the PHY layer pad is included after the PHY tail bits. 22.The apparatus of claim 13, wherein the processor electronics are furtherconfigured to generate, at a MAC layer, the one or more MAC data unitsand the MAC layer pad, wherein the MAC layer pad extends past a lastsymbol boundary of the PHY frame, and reduce, at a PHY layer, the lengthof the MAC layer pad at a PHY layer to not extend past the last symbolboundary of the PHY frame.
 23. The apparatus of claim 13, wherein theprocessor electronics are further configured to receive the data forwireless communication devices, transmit spatially steered frames thatconcurrently provide the data to the wireless communication devices,wherein a steered frame of the steered frames includes the one or moreMAC data units, the MAC layer pad, and the PHY layer pad, and whereinends of the steered frames are aligned to have the same length, which issignaled by an omni-directional PHY signaling field that is common tothe steered frames.
 24. A system comprising: circuitry to transmit andreceive wireless communication signals; and processor electronicsconfigured to obtain data for a transmission to a wireless communicationdevice, include one or more medium access control (MAC) data units in aphysical (PHY) frame, wherein the one or more MAC data units encapsulatethe data, determine a length of a MAC layer pad based on a number ofsymbols associated with the PHY frame, include, in response to thelength of the MAC layer pad being greater than zero, the MAC layer padin the PHY frame after the one or more MAC data units, determine alength of a PHY layer pad based on remaining available bits in the PHYframe, and include, in response to the length of the PHY layer pad beinggreater than zero, the PHY layer pad in the PHY frame after the MAClayer pad.
 25. The system of claim 24, wherein the one or more MAC dataunits are MAC protocol data units (MPDUs) that are included in the PHYframe in an aggregated MPDU (A-MPDU), and wherein the processorelectronics are further configured to include one or more paddingdelimiters after a last non-zero-length A-MPDU subframe in the A-MPDU,wherein each of the one or more padding delimiters are four octets inlength, and include a MAC pad after the one or more padding delimiters,wherein the MAC pad is an integer number of octets in length, which isless than four octets, wherein the MAC layer pad includes the one ormore padding delimiters and the MAC pad.
 26. The system of claim 25,wherein the one or more padding delimiters include an end-of-frame flagto inform the wireless communication device to stop receiving aremaining portion of the PHY frame.
 27. The system of claim 26, whereinthe processor electronics are further configured to receive the data forwireless communication devices, transmit spatially steered frames thatconcurrently provide the data to the wireless communication devices,wherein a steered frame of the steered frames includes the one or moreMAC data units, the MAC layer pad, and the PHY layer pad, and whereinends of the steered frames are aligned to have the same length, which issignaled by an omni-directional PHY signaling field that is common tothe steered frames.